The invention relates to an electromechanically actuated disc brake having a self-boosting design.
Disc brakes, which reduce the power demand of the drive, by utilizing self-boosting effects have been known for a long time.
Typical examples of brakes of this type are described for example in DE 101 56 348 C1, in the slightly older, generic patent application DE 101 39 913.8 and in DE 10 2005 030 618.7.
Brakes of such design have in common the fact that the support of the tangential forces, which act on the brake pad, takes place by way of a wedge or ramp system, which provides the self-boosting action.
Here, the friction force which acts on the brake pad is transmitted by a part, which is connected to the brake pad and which is movable with the latter in the tangential direction, of the self-boosting device via rolling bodies or by way of sliding contact against a part, which is stationary in the tangential direction, of the self-boosting device.
In brakes which are not fitted with a wear adjusting device, the transmission of force takes place directly from the stationary part to the brake caliper.
However, if a wear adjusting device is used, as is conventional in disc brakes for utility vehicle applications, it is advantageous if a part, which is stationary during braking processes, of the self-boosting device is connected to pistons of the wear adjusting device which are adjustable in length and which are provided with a guide system via which tangential forces are dissipated to the brake caliper.
As a result of the transmission of the high tangential forces, which may be greater than 80 kN in the case of a disc brake for heavy utility vehicles, wear to the sensitive components of the wear adjusting device occurs and it is necessary for those components to be dimensioned to be excessively large in relation to their actual purpose.
In the case of a design of the brake as a sliding-caliper brake, the described problem occurs to an increased extent since the tangential forces must, in this case, additionally be transmitted from the brake caliper via its sliding guide to the axially fixed brake carrier.
FIG. 3 of WO 03/071150 A 1 describes a brake design in which the tangential forces of the stationary part of the self-boosting device are transmitted, so as to be supported, directly to the brake frame. The stationary component has a very massive design since the actuating force is generated between the component and the pressure plate. In the case of the design as a sliding-caliper brake, it is necessary here for the tangential forces to be dissipated via the sliding guide of the brake caliper.
The invention is based on the object of further developing a self-boosting disc brake such that sensitive components of a wear adjusting device and/or of a caliper sliding guide are less highly loaded.
The invention achieves this, and other, objects by providing a self-boosting electromechanically actuable disc brake having an axially fixed component, a brake caliper which is movable relative to the axially fixed component, at least one application-side and one reaction-side brake pad, and a brake disc. An electromechanical drive and a brake application device for applying the brake pad are provided, which brake application device has a self-boosting device. At least one wear adjusting device for adjusting brake pad and/or disc wear is also provided. The self-boosting device includes a component which is stationary during braking processes but which is movable parallel to the brake disc rotational axis during adjusting movements, the component being connected to or being part of the wear adjusting device. The component, which is stationary during braking processes, of the self-boosting device is held, with a small degree of play, parallel to the brake disc rotational axis between guide surfaces of the axially fixed component of the brake, such that, during braking processes, the tangential forces which occur are transmitted, so as to be supported, directly from the stationary component of the self-boosting device to the axially fixed component of the brake.
According thereto, the stationary component of the self-boosting device, which stationary component is connected to the adjusting device, is held, with a small degree of play, parallel to the brake disc rotational axis between guide surfaces of the axially fixed component of the brake, in such a way that, during braking processes, the tangential forces which occur are transmitted, so as to be supported, directly from the stationary component of the self-boosting device to the axially fixed component of the brake.
In this way, a disc brake of a self-boosting design is created in which the transmission of the tangential force, which is introduced from the brake pad into the self-boosting device, to the axially fixed component of the brake takes place such that sensitive components of the wear adjusting device and/or of the caliper sliding guide are no longer acted upon by the forces.
The invention is particularly advantageously applied to sliding-caliper brakes. In such a case, the axially fixed component is preferably the brake carrier of the sliding-caliper brake. In contrast to conventional sliding-caliper disc brakes for utility vehicles, therefore, it is no longer the brake pad which is supported directly on the brake carrier, but rather one or more adjusting devices formed as a pressure ram.
The sliding caliper itself, the wear adjusting system which is situated in the caliper, and the sliding guide of the caliper are relieved of the load of the occurring tangential forces, since those forces are dissipated directly from the guide plate to the brake carrier.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.